अहो बत महत्पापं कर्तुं व्यवसिता वयम्। यद्राज्यसुखलोभेन हन्तुं स्वजनमुद्यताः ॥

aho bata mahat pāpaṁ kartuṁ vyavasitā vayam yad rājya-sukha-lobhena hantuṁ sva-janam udyatāḥ

Alas! in committing a great sin are we engaged, we who are endeavouring to kill our kindred from greed of the pleasures of kingship.

In plain words: Arjuna cries out that they are about to commit a great sin. He says they are ready to kill their own relatives just because they want the pleasures of being king.